Bag-less, portable hand-held vacuums of the corded and cordless varieties are well known in the art and typically include a fan for producing an air flow, a dirt cup for retention of the material, such as dirt, dust and debris, that is drawn into the vacuum and a filter that prevents this material from being drawn into the fan. The filter may include a single filter media, which may be a fabric or paper material, or may utilize several materials that are arranged in series so as to progressively filter the air flow.
As is well known in the art, the users of such bag-less portable hand-held vacuums tend to be less than diligent in the maintenance of such vacuums so that such vacuums are frequently operated with clogged and/or dirty filters. Operation of a bag-less hand-held vacuum in this manner impairs the performance of the vacuum, increases the load on the fan motor and fan (which tends to reduce the life of these components), and in the case of cordless vacuums, tends to reduce both the life of its rechargeable battery and the duration with which the vacuum may be operated on a single charge.
In view of the tendency of consumers to operate such vacuums with clogged or dirty filters, the industry has focused on improved filter configurations that utilize several filtering stages that commence with a relatively coarse plastic or wire screen and terminate in a relatively fine fabric or paper material that is configured to prevent relatively small sized particles from entering the fan. We have found that although the advancements in filter technology for such vacuums have generally increased the time interval that is permissible between filter cleanings, these advancements have thus far not eliminated the necessity of such cleanings.